The objective of this study is a definition of a relationship of bile acids or their derivatives to the etiology of colorectal cancer. The project will extend the investigation of dietary effects on the quantity and nature of bile acids in enterohepatic circulation of the rat by analysis of small samples of rat bile obtained at regular intervals. Identification and quantitation of bile acids will be affected by newly developed methods involving high pressure liquid chromatography, gas chromatography, the combination of gas chromatography-mass spectrometry with an on-line computer, and enzymatic assay.